1. Field of the Invention
This invention relates generally to a method of treating, preventing or inhibiting leishmaniasis in a subject. In particular, the invention relates to a method of treating, preventing or inhibiting leishmaniasis in a subject by the administration of at least one reversed amidine.
2. Description of the Related Art
Parasitic diseases have an overwhelming impact on public health in developing areas of the world. One such disease is leishmaniasis, a spectrum of disease in man that is life-threatening in its most severe form. Leishmaniasis is caused by several species of Leishmania. These unicellular organisms of the order Kinetoplastida are related to trypanosomes, the causative organisms of Sleeping Sickness in Africa and Chagas"" disease in South America. Leishmania parasites commonly exist in two distinct forms, the motile promastigote of the insect vector and the sessile amastigote present in the mammalian host. Promastigotes are transmitted to humans by the bite of infected phlebotomine sandflies, which are found throughout the world""s inter-tropical and temperate regions. Upon delivery into the mammalian host, promastigotes infect macrophages of the reticuloendothelial system and transform into amastigotes.
Three main clinical variants of this disease are known: cutaneous, mucocutaneous, and visceral. Cutaneous leishmaniasis can manifest itself as a single skin ulceration at the site of the sandfly bite appearing soon after infection or month later as disseminated lesions. Mucocutaneous syndrome develops as the cutaneous form, but progresses months or years later to lesions of the mouth, nose, or pharynx. The major long-term effects of cutaneous and mucocutaneous disease are scarring. Visceral leishmaniasis has an incubation period of 3-6 months and involves the reticuloendothelial system.
Clinical manifestations include enlargement of the liver and spleen, fever, anemia, and weight loss. Symptomatic visceral disease often ends in death in the absence of treatment. In recent years, the coexistence of HIV and Leishmania species causing visceral disease has resulted in several hundreds of cases of dually infected individuals. See Berman, J. D., (1997) Clin. Infect. Dis. 24:684. The World Health Organization recently estimated in 2000 that leishmaniasis affects people in 88 countries, with 350 million at risk of contracting the disease and about two million new cases each year. The devastating impact of this disease is exemplified by the recent epidemic of visceral leishmaniasis in the Sudan, which claimed an estimated 100,000 lives. See Seaman, J., et al. (1996) Int. J. Epidemiol. 25:862. This disease is frequently a threat in military operations, as demonstrated by the outbreak of viscerotropic leishmaniasis during the Gulf War. See Magill, J., et al. (1993) N Engl J Med 328:1383.
Unfortunately, few drugs or compounds exist which exhibit anti-leishmanial activity in vitro or in vivo. Pentavalent antimonial compounds have been the first line drugs for leishmaniasis since the 1940""s, and two forms of Sb(V) are commonly used. Sodium stibogluconate (Pentostam(copyright) (Wellcome Foundation, London, England)) and meglumine antimoniate (Glucantime(copyright) (Rhone Poulenc, Paris, France)) are prescribed according to Sb(V) content and are generally considered to be equivalent in terms of efficacy and toxicity. These drugs must be given by injection over a 20-28 day course. Unfortunately, the antimonial compounds exhibit side effects such as nausea and severe toxic side effects, such as hepatitis, nephritis, and myocarditis. See Berman, J. D., (1997). Further, reports of unresponsiveness to antimony treatment are becoming more frequent. See Olliaro, P., et al. (1993) Parasitol. Today 9:323. Moreover, there is a strong correlation between clinical resistance to Pentostam(copyright) and decreased in vitro susceptibility to this drug. See Lira, R., et al. (1999) J. Infect. Dis. 180:564.
Amphotericin B is also used as a treatment for visceral leishmaniasis. Past implementation of this drug was limited to toxic side reactions including fever, bone pain, and decreased renal function. Although new clinical formulations of amphotericin B in lipid complexes are less toxic than amphotericin B, these new clinical formulations are more expensive, and a major problem in treating visceral leishmaniasis in developing countries. Also, amphotericin B and amphotericin B-lipid complexes do not appear to be suitable for treating nonvisceral disease. See Berman, J. D., (1997). Oral miltefosine has shown some promise in the treatment of visceral leishmaniasis in India, however, efficacy against cutaneous disease has yet to be reported and miltefosine has not yet been approved for clinical use in any country. See Jha, T., et al. (1999) N. Eng. J. Med. 341:1795 and Sundar, S., et al. (2000) Clin. Infect. Dis. 31:1110.
Other compounds such as pentamidine and analogues thereof exhibit some anti-leishmanial activity. See U.S. Pat. No. 5,202,320; Steck, E. A., et al. (1981) Exp. Parasitol. 52(3):404-413; and Berman, J. D., et al. (1988) Rev. Infect. Dis. 10(3):560-586. Pentamidine is frequently used for the treatment of leishmaniasis and is currently being evaluated by the U.S. Army for use on troops infected with Leishmania. See Hellier, I., et al. (2000) Dermatology 200:120 and Soto, J., et al. (1994) Am. J. Trop. Med. Hyg. 50:107. However, the drawbacks of the clinical use of pentamidine and pentamidine analogues are the route of administration (injection) and the toxicity of the compounds. Administration by injection increases the expense of the treatment and makes the use of the drug less practical in developing nations where cost is a major factor. The clinical side effects of pentamidine include renal and hepatic toxicity, pancreatitis, hypotension, dysglycemia, and cardiac abnormalities. See Berman, J. D., (1997) and Goa, K., et al. (1987) Drugs 33:242.
Thus, a need exists for an anti-leishmanial agent for the treatment of leishmaniasis.
The present invention generally relates to compounds and methods for the treatment of leishmaniasis.
In some embodiments, the present invention provides a method for treating, preventing or inhibiting leishmaniasis in a subject comprising administering to the subject a therapeutically effective amount of at least one compound having the structural formula 
wherein Y is a heteroatom; R1 and R2 are independently H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group; and X1, X2, and X3 are independently H or an alkyl, alkoxy, halo, amino, alkylamino, dialkylamino, acylamino, alkylthio, sulfonyl, cyano, carboxy, alkoxycarbonyl, or carbamoyl group. In preferred embodiments, Y is O or S, R1 and R2 are independently H, phenyl, cyclohexyl, quinolyl, pyridinyl, or methylpyridinyl, and X1, X2, and X3 are independently H, Cl, amino, methyl, methoxy, ethoxy, or propan-2-oxy. Preferably, X1, X2, and X3 are each independently at positions 2, 3, 5, or 6 of the phenyl rings, more preferably, X1 and X2 are each independently at positions 2 or 3. Preferably, the subject is mammalian, more preferably, the subject is human.
In some embodiments, the method further includes administering a supplementary active compound to the subject. The supplementary active compound may be sodium stibogluconate such as Pentostam(copyright), meglumine antimoniate such as Glucantime(copyright), pentamidine, amphotericin B, miltefosine, paromomycin, and the like.
In preferred embodiments, the compound is
2,5-Bis[4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[4-(benzimidoylamino)phenyl]furan;
2,5-Bis[4-(cyclohexylimino)aminophenyl]furan;
2,5-Bis[4-(acetimidoyl)aminophenyl]furan;
2,5-Bis[4-(benzimidoyl)amino-2-methylphenyl]furan;
2,5-Bis[2-methyl-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-methyl-4-(2-quinolylimino)aminophenyl]furan;
2,5-Bis[2-methyl-4-(5-methyl-2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-methoxy-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-chloro-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2,6-dimethyl-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis(4-guanidino-2-methylphenyl)furan;
2,5-Bis(4-guanidino-2-trifluoromethylphenyl)furan;
2,5-Bis[2-methyl-4-(2-pyridylimino)aminophenyl]thiophene;
2-[5(6)-(2-Pyridylimino)amino-2-benzimidazoyl]-5-[4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-methyl-4-(2-quinolylimino)aminophenyl]furan;
2-(4-Guanidinophenyl)-4-(3-guanidinophenyl)furan;
2,5-Bis(4-guanidino-2,6-dimethylphenyl)furan;
2,5-Bis[2-ethoxy-4-(2-pyridylimino)aminophenyl)furan;
2,5-Bis[2,3-dimethyl-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis(4-guanidino-2,3-dimethylphenyl)furan;
2,5-Bis[2-methyl-4-(6-methyl-2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-hydroxy-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-methoxy-5-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-(2-propoxy)-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis[2-(2-propoxy)-4-(5-methyl-2-pyridylimino)aminophenyl]furan;
2,5-Bis[3-ethoxy-4-(2-pyridylimino)aminophenyl]furan;
2,5-Bis(2-ethoxy-4-guanidinophenyl)furan;
2,5-Bis[4-guanidino-2-(2-propoxy)phenyl]furan;
2,5-Bis(4-guanidino-3-methoxyphenyl)furan;
2,5-Bis(3-ethoxy-4-guanidinophenyl)furan;
2,5-Bis[3-methoxy-4-(2-pyridylimino)aminophenyl]furan
2,5-Bis(4-guanidino-2-methylphenyl)thiophene; or
2,5-Bis(4-guanidinophenyl)thiophene.
In some embodiments, the present invention relates to a method for treating, preventing or inhibiting leishmaniasis in a subject comprising administering to the subject a therapeutically effective amount of at least one reversed amidine. Preferably, the subject is mammalian, more preferably, human.
In some embodiments, the present invention relates to a method for treating, preventing or inhibiting leishmaniasis in a subject comprising administering to the subject a therapeutically effective amount of at least one compound comprising at least one reversed amidine group having the structural formula 
wherein R1 is H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group. Preferably, the subject is mammalian, more preferably, human.
In other embodiments, the present invention provides a method for treating, preventing or inhibiting a disease or disorder associated with leishmaniasis in a subject comprising administering to the subject a therapeutically effective amount of at least one compound having the structural formula 
wherein Y is a heteroatom; R1 and R2 are independently H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group; and X1, X2, and X3 are independently H or an alkyl, alkoxy, halo, amino, alkylamino, dialkylamino, acylamino, alkylthio, sulfonyl, cyano, carboxy, alkoxycarbonyl, or carbamoyl group. In preferred embodiments, Y is O or S, R1 and R2 are independently H, phenyl, cyclohexyl, quinolyl, pyridinyl, or methylpyridinyl, and X1, X2, and X3 are independently H, Cl, amino, methyl, methoxy, ethoxy, or propan-2-oxy. Preferably, X1, X2, and X3 are each independently at positions 2, 3, 5, or 6 of the phenyl rings, more preferably, X1 and X2 are each independently at positions 2 or 3. The disease or disorder may be cutaneous leishmaniasis, mucocutaneous leishmaniasis, or visceral leishmaniasis. Preferably, the subject is mammalian, more preferably, human.
In some embodiments, the present invention relates to a method of reducing, suppressing or inhibiting an amount of a parasite in a target comprising administering to the target an effective amount of at least one compound having the structural formula 
wherein Y is a heteroatom; R1 and R2 are independently H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group; and X1, X2, and X3 are independently H or an alkyl, alkoxy, halo, amino, alkylamino, dialkylamino, acylamino, alkylthio, sulfonyl, cyano, carboxy, alkoxycarbonyl, or carbamoyl group. In preferred embodiments, Y is O or S, R1 and R2 are independently H, phenyl, cyclohexyl, quinolyl, pyridinyl, or methylpyridinyl, and X1, X2, and X3 are independently H, Cl, amino, methyl, methoxy, ethoxy, or propan-2-oxy. Preferably, X1, X2, and X3 are each independently at positions 2, 3, 5, or 6 of the phenyl rings, more preferably, X1 and X2 are each independently at positions 2 or 3. In preferred embodiments, the reversed amidine compound reduces, suppresses or inhibits parasite growth, infection, or proliferation by about 50% at a concentration of about 10.0 xcexcg/ml or less, about 7.0 xcexcg/ml or less, about 5.0 xcexcg/ml or less, about 2.5 xcexcg/ml or less, or about 1.0 xcexcg/ml or less. In preferred embodiments, the parasite is a Leishmania parasite. In other preferred embodiments, the compound reduces, suppresses or inhibits L. mexicana by about 50% at a concentration of about 10.0 xcexcg/ml or less, preferably less than about 1.0 xcexcg/ml. In other embodiments, the compound reduces, suppresses or inhibits L. donovani at a concentration of about 10.0 xcexcg/ml or less, preferably less than about 1.0 xcexcg/ml. In some preferred embodiments, the reverse amidine compound reduces, suppresses, or inhibits Leishmania parasite growth, infection, or proliferation by about 50% at a concentration of about 0.1 xcexcg/ml to about 1.0 xcexcg/ml. The target is a mammal or tissues or cells derived therefrom. Preferably, the mammal is human.
In other embodiments, the present invention provides a pharmaceutical composition for treating, preventing or inhibiting leishmaniasis in a subject comprising a therapeutically effective amount of at least one compound having the structural formula 
wherein Y is a heteroatom; R1 and R2 are independently H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group; and X1, X2, and X3 are independently H or an alkyl, alkoxy, halo, amino, alkylamino, dialkylamino, acylamino, alkylthio, sulfonyl, cyano, carboxy, alkoxycarbonyl, or carbamoyl group. In preferred embodiments, Y is O or S, R1 and R2 are independently H, phenyl, cyclohexyl, quinolyl, pyridinyl, or methylpyridinyl, and X1, X2, and X3 are independently H, Cl, amino, methyl, methoxy, ethoxy, or propan-2-oxy. Preferably, X1, X2, and X3 are each independently at positions 2, 3, 5, or 6 of the phenyl rings, more preferably, X1 and X2 are each independently at positions 2 or 3. Preferably, the subject is mammalian, more preferably the subject is human.
In some embodiments, the present invention provides a kit comprising at least one compound having the structural formula 
wherein Y is a heteroatom; R1 and R2 are independently H or an alkyl, cycloalkyl, heterocycloalkyl, aryl, amino or heteroaryl group; and X1, X2, and X3 are independently H or an alkyl, alkoxy, halo, amino, alkylamino, dialkylamino, acylamino, alkylthio, sulfonyl, cyano, carboxy, alkoxycarbonyl, or carbamoyl group; and instructions for use of the compound for the treatment of a subject having a disease or disorder associated with leishmaniasis.